An image forming apparatus reproduces an image signal (image data) which has been read from a document on a recording medium such as a sheet. Such an image forming apparatus includes a printer, a copying machine, and other apparatuses.
In such an image forming apparatus, in order to maintain the image quality of a reproduced image desirably, it is required to set the respective contents of processing to be carried out by an image processing section and an image recording section according to the document image. Such a setting of the processing contents is required, for example, for the case where the amount of light exposed on a document should increased or decreased according to the image density of the document, or for the case where the contrast adjustment should be changed by the image recording section for a photographic image having tones and a character image having no tones.
For this reason, an operation panel of the image forming apparatus is provided with (1) keys for inputting image forming conditions such as image density and a contrast and (2) mode changing keys for manually or automatically setting the image forming conditions.
In the case of sequentially carrying out an image forming process on a plurality of documents by an automatic document transporting device, it is possible that the image density differs in the plurality of documents, and a document having a photographic image and a document having a character image coexist. In this case, in order to obtain a high quality copy image (reproduced image) for each document, it is required to individually set the image forming conditions for each document.
However, if the image forming conditions are to be set solely by the operation of the keys on the operation panel, the operation by an operator becomes complicated when carrying out the image forming process. This presents a problem that it is difficult to completely prevent the deterioration of the image quality of the copy image due to an operational error of the operation panel, and the efficiency of the image forming process is lowered, accordingly. Particularly, in a color image forming apparatus for reproducing a color image, it is required to set various image forming conditions such that it is too complicated and difficult to change and set the image forming conditions for each document.
As a counter measure, Japanese Unexamined Patent publication No. 197965/1988 (Tokukaisho 63-197965) (corresponding to U.S. Pat. No. 4,716,438) discloses an arrangement wherein a sheet called a separator provided with a control code (separate body) is read with a document so as to set image forming conditions based on the control code which has been read from the sheet.
Also, Japanese Unexamined Patent publication No. 578/1989 (Tokukaisho 64-578) discloses an arrangement wherein a bar code control pattern is provided on the front end of a document so as to set image forming conditions based on the contents of the bar code thus read as a partial image of the document.
Further, Japanese Unexamined Patent publication No. 157866/1990 (Tokukaihei 2-157866) discloses an arrangement wherein a specifying pattern for specifying how the operation should be carried out is provided on a document so as to set image forming conditions based on the specifying pattern.
Furthermore, Japanese Unexamined Patent publication No. 281474/1992 (Tokukaihei 4-281474) (corresponding to U.S. Pat. No. 5,296,896) discloses an arrangement wherein coded image forming conditions are provided on a portion of a transfer sheet so as to set image forming conditions based on the contents of the code thus read by reading means.
However, according to the inventions disclosed in the above-mentioned Japanese Unexamined Patent publication No. 578/1989 (Tokukaisho 64-578) and Japanese Unexamined Patent publication No. 157866/1990 (Tokukaihei 2-157866), information indicative of image forming conditions is provided on an image formed surface of a document. This presents problems that a portion of a document image is not reproduced, and the information thus provided is reproduced as a partial document image. This interferes with observing of a reproduced image so as to lower the quality of the copy image. Therefore, the inventions disclosed in the above-mentioned publications are not suitable for a color document image in particular in which a high image quality is demanded.
Also, according to the invention disclosed in Japanese Unexamined Patent publication No. 197965/1988 (Tokukaisho 63-197965) , the control code indicative of the image forming conditions is provided on a control sheet which is different from a document. Thus, the control sheet can easily be lost or misused, thereby presenting the problem that the control sheet is not easy-to-use.
Further, according to the invention disclosed in Japanese Unexamined Patent publication No. 281474/1992 (Tokukaihei 4-281474), the code indicative of the image forming conditions is provided on a sheet (transfer sheet). This presents a problem that the copy image partially overlaps the code, and the copy image and the code become close to one another so as to make the copy image difficult to be recognized, thereby resulting in that the image quality deteriorates.